Search results for "Quaternary"

tert-Butoxyl radicals generate mainly 7,8-dihydro-8-oxoguanine in DNA.

2000

Abstract Like hydroxyl radicals, alkoxyl radicals have been implicated in the generation of cellular oxidative DNA damage under physiological conditions; however, their genotoxic potential has not yet been established. We have analyzed the DNA damage induced by a photochemical source of tert- butoxyl radicals, the water soluble peroxy ester [4-( tert -butyldioxycarbonyl)benzyl]triethylammonium chloride (BCBT), using various repair endonucleases as probes. The irradiation (UV 360 ) of BCBT in the presence of bacteriophage PM2 DNA was found to generate a DNA damage profile that consisted mostly of base modifications sensitive to the repair endonuclease Fpg protein. Approximately 90% of the mo…

Stereoselective Access to Fluorinated and Non-fluorinated Quaternary Piperidines: Synthesis of Pipecolic Acid and Iminosugar Derivatives

2012

The preparation of optically pure quaternary piperidines, both fluorinated and non-fluorinated, has been achieved from a chiral imino lactone derived from (R)-phenylglycinol. In the case of the fluorinated derivatives, the addition of (trifluoromethyl)trimethylsilane (TMSCF(3)) followed by iodoamination and migration of the CF(3) group allowed access to four derivatives of α-(trifluoromethyl)pipecolic acid. A theoretical study of the CF(3)-group rearrangement has been carried out to help establish the reaction mechanism of this uncommon transformation. Moreover, a route to trifluoromethyl-substituted iminosugars was also developed through the diastereoselective dihydroxylation of suitable s…

Interaction of wild-type and naturally occurring deleted variants of hepatitis B virus core polypeptides leads to formation of mosaic particles

2000

AbstractThe simultaneous presence of hepatitis B virus (HBV) genomes carrying wild-type (wt) and in-frame deleted variants of the HBV core gene has been identified as a typical feature of HBV-infected renal transplant patients with severe liver disease. To investigate possible interactions of wt and deleted core polypeptides a two-vector Escherichia coli expression system ensuring their concomitant synthesis has been developed. Co-expression of wt and a mutant core lacking 17 amino acid residues (77–93) within the immunodominant region led to the formation of mosaic particles, whereas the mutant alone was incapable of self-assembly.

Mosaic particles formed by wild-type hepatitis B virus core protein and its deletion variants consist of both homo- and heterodimers.

2003

AbstractCo-expression in Escherichia coli of wild-type (wt) hepatitis B virus core protein (HBc) and its naturally occurring variants with deletions at amino acid positions 77–93 or 86–93 leads to formation of mosaic particles, which consist of three dimer subunit compositions. These compositions are wt/variant HBc heterodimers and two types of homodimers, formed by wt HBc or the variant HBc themselves. Mosaic particles were found also when both HBc deletion variants 77–93 and 86–93 were co-expressed in E. coli. These findings are discussed in terms of their significance for hepatitis B virus pathogenesis and prospective use of mosaic particles in vaccine development.

Correction: Phylogeny of the Eurasian Wren Nannus troglodytes (Aves: Passeriformes: Troglodytidae) reveals deep and complex diversification patterns …

2020

The Mediterranean Basin represents a Global Biodiversity Hotspot where many organisms show high inter- and intraspecific differentiation. Extant phylogeographic patterns of terrestrial circum-Mediterranean faunas were mainly shaped through Pleistocene range shifts and range fragmentations due to retreat into different glacial refugia. Thus, several extant Mediterranean bird species have diversified by surviving glaciations in different hospitable refugia and subsequently expanded their distribution ranges during the Holocene. Such a scenario was also suggested for the Eurasian Wren (Nannus troglodytes) despite the lack of genetic data for most Mediterranean subspecies. Our phylogenetic mult…

STOP 1: Lower Gauja spillway valley at Sigulda

2014

STOP 9: Upper Daugava spillway valley and associated gully network at Vasargelišķi

2014

Growth and macromolecular content of the dimorphic fungus Aureobasidium pullulans and the effect of hydroxyurea and other inhibitors

1988

The growth kinetics and the macromolecular content of the yeast and ethanol-induced hyphal forms of Aureobasidium pullulans were studied. During the morphological transition from yeasts to hyphae, both the protein and RNA content decreased significantly, the mycelial form containing only 76% of the amount of protein in the yeasts, and 38% of the RNA. The DNA was the only component tested whose level increased during the transition. Among several compounds inhibiting macromolecular synthesis, only hydroxyurea showed a remarkable effect on the morphology of A. pullulans, inducing the mycelial morphology. The macromolecular composition of hydroxyurea-treated cultures changed with time in a way…

Nouvelles perspectives concernant la structure et la fonction du domaine carboxyl terminal de Hfq

2015

Accumulating evidence indicates that RNA metabolism components assemble into supramolecular cellular structures to mediate functional compartmentalization within the cytoplasmic membrane of the bacterial cell. This cellular compartmentalization could play important roles in the processes of RNA degradation and maturation. These components include Hfq, the RNA chaperone protein, which is involved in the post-transcriptional control of protein synthesis mainly by the virtue of its interactions with several small regulatory ncRNAs (sRNA). The Escherichia coli Hfq is structurally organized into two domains. An N-terminal domain that folds as strongly bent β-sheets within individual protomers to…

Effect of pH and HNO2 concentration on the activity of ammonia-oxidizing bacteria in a partial nitritation reactor

2013

Ammonia-oxidizing bacteria (AOB) are very sensitive to environmental conditions and wastewater treatment plant operational parameters. One of the most important factors affecting their activity is pH. Its effect is associated with: NH3/NH4 þ and HNO2/NO2 chemical equilibriums and biological reaction rates. The aim of this study was to quantify and model the effect of pH and free nitrous acid (FNA) concentration on the activity of AOB present in a lab-scale partial nitritation reactor. For this purpose, two sets of batch experiments were carried out using biomass from this reactor. Fluorescent in situ hybridization analysis showed that Nitrosomona eutropha and Nitrosomona europaea species we…